block: mark queue init done at the end of blk_register_queue

Mark queue init done when everything is done well in blk_register_queue(), so that wbt_enable_default() can be run quickly without any RCU period involved since adding rq qos requires to freeze queue. Also no any side effect by delaying to mark queue init done. Reported-by: Yi Zhang <[email protected]> Cc: Bart Van Assche <[email protected]> Signed-off-by: Ming Lei <[email protected]> Reviewed-by: Bart Van Assche <[email protected]> Tested-by: Yi Zhang <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Jens Axboe <[email protected]>
tobetter · Jun 16, 2021 · a72c374 · a72c374
1 parent 2cafe29
commit a72c374
Showing 1 changed file with 15 additions and 14 deletions.
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
@@ -866,20 +866,6 @@ int blk_register_queue(struct gendisk *disk)
 		  "%s is registering an already registered queue\n",
 		  kobject_name(&dev->kobj));
 
-	/*
-	 * SCSI probing may synchronously create and destroy a lot of
-	 * request_queues for non-existent devices.  Shutting down a fully
-	 * functional queue takes measureable wallclock time as RCU grace
-	 * periods are involved.  To avoid excessive latency in these
-	 * cases, a request_queue starts out in a degraded mode which is
-	 * faster to shut down and is made fully functional here as
-	 * request_queues for non-existent devices never get registered.
-	 */
-	if (!blk_queue_init_done(q)) {
-		blk_queue_flag_set(QUEUE_FLAG_INIT_DONE, q);
-		percpu_ref_switch_to_percpu(&q->q_usage_counter);
-	}
-
 	blk_queue_update_readahead(q);
 
 	ret = blk_trace_init_sysfs(dev);
@@ -938,6 +924,21 @@ int blk_register_queue(struct gendisk *disk)
 	ret = 0;
 unlock:
 	mutex_unlock(&q->sysfs_dir_lock);
+
+	/*
+	 * SCSI probing may synchronously create and destroy a lot of
+	 * request_queues for non-existent devices.  Shutting down a fully
+	 * functional queue takes measureable wallclock time as RCU grace
+	 * periods are involved.  To avoid excessive latency in these
+	 * cases, a request_queue starts out in a degraded mode which is
+	 * faster to shut down and is made fully functional here as
+	 * request_queues for non-existent devices never get registered.
+	 */
+	if (!blk_queue_init_done(q)) {
+		blk_queue_flag_set(QUEUE_FLAG_INIT_DONE, q);
+		percpu_ref_switch_to_percpu(&q->q_usage_counter);
+	}
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(blk_register_queue);